Human Performance and Limitations
This domain tests how the pilot's body and mind fail, and how to recognise and manage those failures. Expect physiology, sensory illusions, fatigue, stress and decision-making.
Physiology
- Hypoxia: insufficient oxygen at the tissues. Symptoms include euphoria, tingling, poor judgement and cyanosis. Treat with 100 percent oxygen and descent.
- Time of useful consciousness falls rapidly with altitude; above FL 250 it is measured in minutes.
- Hyperventilation produces dizziness, tingling and blurred vision and can mimic hypoxia - the correct response is to control breathing, and if in doubt treat as hypoxia with oxygen.
- Decompression sickness follows nitrogen bubbles after rapid decompression; treat with descent and oxygen.
Sensory illusions
- Somatogravic illusion: acceleration is misread as pitch-up, so the pilot pushes forward during a night go-around - a classic fatal trap.
- Black-hole approach: a narrow, poorly lit runway at night makes the aircraft appear too high, producing a low approach.
- The leans, autokinesis and Coriolis illusion all argue for trusting instruments, not sensations.
Vision
- Use off-centre viewing at night; the fovea is poor in low light. Allow 30 minutes for dark adaptation and avoid bright light.
- Empty-field myopia makes distant objects appear closer in featureless haze - common over desert and sea.
Fitness and judgement
- Fatigue, circadian low points, dehydration (high risk in Oman heat), alcohol, medication and stress all degrade decision-making. Declare unfit rather than fly.
Worked example
On a dark go-around after a night approach, you feel the aircraft pitching up sharply. This is the otolith organs responding to linear acceleration, not a real attitude change. Cross-check the attitude indicator and hold the required pitch attitude.
Traps
Treating hyperventilation and hypoxia as mutually exclusive; assuming you will feel hypoxic - euphoria prevents self-detection.